Inherited criminality

• Lombroso 


  suggested that criminals had distinct features,the 'atavistic form'
• Sheldon 


  linked criminal behaviour to body types,claiming mesomorphs(muscular and athletic) were more prone to crime
• Lombroso and Sheldon theories have been discredited as recent interest in genetics has prompted some to explore a genetic basis of criminal behaviour
• Rosanoff et al


  97 twin pairs were examined

  Male twins,the concordance rate was 67% for identical twins(MZ) and 13% for non-identical twins(DZ)
• Raine


  reviewed twin studies and found MZ twins had a higher average concordance rate(52%) compared to DZ (21%)
• Dalgard and Kringlen


  examined 49 male MZ twins and 89 same-sex DZ twins.

  Found no significant difference in concordance rates for crime,whether broadly or strictly defined.

  22% for broadly defined and 26% for strictly defined.
• specific genes influencing such behaviour should be identifiable
• 2 genes have been linked to criminal behaviour

  MAOA gene

  CDH13 gene
• MAOA gene


  involves serotonin recycling
• Seo et al


  proposed that low levels of serotonin may lead to impulsive and aggressive behaviour
• Brunner et al


  found a dutch family with aggressive behaviours linked to a mutation of the MAOA gene,causing low serotonin levels
• Tiihonen et al


  studied 900 offenders in Finland,finding low MAOA and CDH13 activity.

  They estimated that 5-10% of violent crime in Finland is due to abnormalities in these genes
• Retz et al


  found an association between a variant of the 5-HTTLPR gene and violent behaviour.
• genes linked to criminal behaviour may affect the brain or neurotransmitters
• Raine


  71 brain imaging studies,showing reduced functioning in the prefrontal cortex for murderers,psychopaths and violent individuals.

  This brain area controls emotions,behaviour and moral conduct.

  Lowered activity can cause impulsiveness and loss of control hence criminality
• Dopamine hyperactivity may enhance the effect of lowered activity in the prefrontal cortex
• Very high and very low levels of noradrenaline are linked to aggression,violence and criminality(Wright et al)
• noradrenaline helps in responding to threats,so low levels might reduce this ability
• inherited personality 


  genes may influence the type of personality inherited by criminals
• Eyesnck

  • extraversion-outgoing,positive
  • neuroticism-incline towards negative emotions
  • psychoticism-egocentric,aggressive,impulsive
  • each trait has a biological basis,mostly innate.He claimed that 67% of the variance in these traits is due to genetic factors
• epigenetics


  genes alone cant determine behaviour
• genes can be switched on and off by epigenomes,influenced by environmental factors-a diathesis stress
• Caspi et al


  studied around 1000 people from the 1970s.

  Men with a low MAOA gene who experienced childhood maltreatment accounted for 44% of violent convictions at 26.

  Even though only 12% had experienced childhood maltreatment.

  Childhood maltreatment may switch on this gene,importance of nature and nurture.